1. Field of the Invention
The present invention relates to a liquid supplying apparatus that supplies a liquid to a print head, and in particular, a liquid supplying apparatus having a liquid housing container detachable from the print head.
2. Description of the Related Art
Ink jet printing apparatuses form an image on a print medium by using a print head to eject a liquid such as ink or a solvent to the print medium. The ink jet printing apparatus includes a serial printer type and a line printer type. A serial printer type printing apparatus forms an image by ejecting the liquid while intermittently conveying the print medium and when the print medium is stopped, moving the print head together with a carriage in a direction orthogonal to a conveying direction. Further, a line printer type printing apparatus has an elongate print head fixed to the main body of the apparatus and consisting of nozzles arranged over at least the maximum print range of the print medium. Thus, the line printer type printing apparatus forms an image by ejecting the liquid from the print head while moving the print medium with respect to the print head.
What is called an on-carriage system is applied to the serial printer type printing apparatus in order to supply the liquid to the print head. With this system, a liquid housing container is integrally and inseparably or separably attached to the print head mounted on a carriage or the like and reciprocate (main scanning). The liquid from the liquid housing container is supplied directly to the print head.
Further, with what is called a tube supplying system, the liquid is supplied by fixedly installing the liquid housing container in another site of the printing apparatus and connecting the liquid housing container and the print head together. The tube supplying system includes a form in which a second liquid housing container functioning as a subtank between the liquid housing container (main tank) and the print head is mounted on the print head or carriage. In this form, the liquid in the second liquid housing container is supplied directly to the print head.
These liquid supplying systems are provided with a mechanism that generates a negative pressure inside the liquid housing container from which the liquid is fed directly to the print head. The negative pressure generating mechanism generates a negative pressure to the extent that the liquid is prevented from leaking inadvertently from a liquid ejecting section of the print head, while the print head can perform an ejecting operation.
When a liquid supply port in the liquid housing container is connected to a liquid supplying section provided in the head, the liquid from the liquid housing container is supplied to nozzles in the print head. Further, an ejection energy generating element (heater or piezoelectric element) is provided in each of the nozzles arranged in the print head; the ejection energy is used to eject ink. The ejection energy generating element is driven in response to a signal from the printing apparatus main body to eject the ink to a print medium to form an image.
Common means for connecting the print head and the liquid housing container together have such configurations as described below.
Japanese Utility Model Application Publication No. 6-34108 discloses an arrangement in a connection structure composed of the liquid supplying tube (needle) and an elastomer (rubber portion), the arrangement allowing the needle to be appropriately inserted into an ink cartridge. In this connection structure, the needle 6 is attached to a needle fulcrum that rotatably supports the needle 6 so as to absorb a shift in or the inclination of the needle. Moreover, in this connection structure, for improved aligning accuracy, alignment is carried out using a needle guide provided at a position closer to the leading end of the needle than to the fulcrum.
This conventional technique executes alignment of the needle with the elastomer near the needle in order to more accurately set the position into which the needle is inserted. After the alignment, the needle is rotatably supported on the needle fulcrum so as to be smoothly guided to a needle seal holding member. However, this conventional technique has no needle seal structure and does not give sufficient considerations for detachment or a fixing technique. Thus, when the ink cartridge is removed, the liquid may leak. Further, since the needle is held by the repulsive force of the elastomer around the needle, the durability of the needle may be affected or creep may occur. Further, the above publication mentions the rotatability of the needle fulcrum, but does not clearly describe a specific mechanism for making the needle fulcrum rotatable. It also fails to clarify the effects of the rotatability.
Further, Japanese Patent Laid-Open No. 1977-150031 discloses a configuration in which concave and convex portions are formed near the head supply port and interlock with concave portions provided on the tank. With this configuration, after the needle is inserted into the tank, the tank itself is rotated to fix the tank and the print head.
The technique disclosed in Japanese Patent Laid-Open No. 1977-150031 requires the housing container to be precisely mounted to the liquid supply tube in order to interlock the concaves in a peripheral portion of the head supplying port with the convexes on the liquid housing container. Further, with this technique, after the tank is inserted around the needle, the tank must be manually rotated. This degrades operability. Moreover, the housing container is cylindrical and a large dead space is thus expected to be created in the printer main body.
Japanese Patent Laid-Open No. 1977-150031 also discloses a seal member 14 that seals the liquid supplying tube to the head. However, the rotation of the container disclosed in this publication is carried out after the container has been completely inserted around the needle. Thus, the seal member may be stuck to the liquid supplying tube to increase an operating force required to rotate the container.
Japanese Patent Laid-Open No. 1999-245431 discloses an arrangement that prevents the leakage of the liquid or installation errors. In this arrangement, a cam surface is provided on the liquid housing container. To install the liquid housing container, a bayonet connector that can rotatably move relative to the main body is rotated along the cam surface to fix the liquid housing container. According to Japanese Patent Laid-Open No. 1999-245431, the rotative moving member, which rotatably moves in association with installation, is provided on the head. The characteristic shape of the rotative moving member allows installation errors to be prevented. Further, rotation of the rotative moving member improves the fixture and sealing.
However, Japanese Patent Laid-Open No. 1999-245431 requires the whole liquid housing container to be rotated when it is to be removed. This degrades the operability. Another problem with Japanese Patent Laid-Open No. 1999-245431 is that since the disclosed housing container is a rectangular parallelepiped, an extremely large dead space may be created when the housing container is removed.
Further, Japanese Utility Model Laid-Open No. 1988-178141 discloses an arrangement intended to prevent the ink from scattering (leaking) by rotating the liquid housing container 1 in order to remove it. In this arrangement, a releasing projection is provided on the tank so that the head and the tank can be rotatably moved relative to each other so as to be separated from each other. When the tank is rotatably moved, the projection operates like a cam to separate the head from the tank.
However, with the structure described in Japanese Utility Model Laid-Open No. 1988-178141 and which allows the attachment and detachment of the liquid housing container to and from the print head, the whole liquid housing container must be rotated during an attaching or detaching operation. This disadvantageously degrades the operability and results in a larger dead space in the main body.
As described above, with the arrangements shown in the above publications and provided for the connection between the print head and the liquid supplying tube to the print head, an increase in installing force required may result from the sticking of the seal portion to the liquid supplying tube to the head, the misalignment between the seal portion and the liquid supplying tube, or the like. Further, disadvantageously, the liquid housing container may be tilted during attachment or detachment, thus degrading the operability.